Nonlinear model characterizing stress-strain relationship and permeability change of contact compression fracture at closing stage

Understanding the stress-strain relationship and permeability change for contact compression fracture at closing stage has been a hot issue for a long time. Previous investigations of this topic were mainly focused on experimental tests; however, theoretical approaches were rarely reported. Based on this, this paper focuses on the contact fracture at closing stage when rock is uniaxially loaded, and then a theoretical model is proposed. Based on the change of fracture elasticity modulus, it shows that as crack apertures are gradually reduced in the loading process, the permeability of rock sample will decrease progressively. This scenario shows that theoretical computation matches well with the experimental results. Finally, the effects of ratio of sample size to fracture aperture (n), pore pressure (P), and initial aperture (b) on stress-strain relationship and permeability change for contact compression fracture at closing stage are analyzed.